Currently we have a Calendars category in Moodle Plugins; however, there is no entry in the Admin block for the Calendar types. There is a section on admin/plugins.php for Calendar types. I propose is adding the element Admin->Plugins->Calendar types and linking to something like admin/plugins.php#plugin_type_cell_calendartype.

On the admin/plugins.php page, many of the plugin types have a link to an admin management page. For example, admin/modules.php for Activities and admin/qtypes.php for Question types. Currently, there is no such page for Calendar types. I am not sure there is a significant need for one but I wanted to mention that it does not currently exist.

MDLSITE: In addition, I would suggest renaming the category from Calendars to Calendar types.